New Map of Saturn Moon Titan Reveals Surprisingly Earth-Like Features

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After meticulously stitching together images that were gathered
over six years by a NASA spacecraft in orbit around Saturn,
astronomers have created a global map of the surface of Titan,
the ringed planet's largest moon, and it features some
surprisingly Earth-like geological features.

An international team of astronomers, led by the University of
Nantes in France, created the striking mosaic of Titan's surface
using infrared images taken by the Visual and Infrared Mapping
Spectrometer (VIMS) aboard NASA's Cassini spacecraft.

The global map and animations were presented Tuesday (Oct. 4) at
the European Planetary Science Congress and the American
Astronomical Society's Division of Planetary Science in Nantes,
France. [ See
global map and video of Titan's surface ]

The researchers used images that were taken during the Cassini
mission's first 70 flybys of Titan. But, piecing together the map
was an intricate and painstaking project because scientists had
to comb through the pictures on a pixel-by-pixel basis to adjust
illumination differences and other distortions caused by
Titan's thick and hazy atmosphere, said Stéphane Le Mouélic,
of the University of Nantes.

"As Cassini is orbiting Saturn and not Titan, we can observe
Titan only once a month on average," Le Mouélic said in a
statement. "The surface of Titan is therefore revealed year after
year, as pieces of the puzzle are progressively put together.
Deriving a final map with no seams is challenging due to the
effects of the atmosphere — clouds, mist etc. — and due to the
changing geometries of observation between each flyby."

Lifting the veil on Saturn's largest moon

Titan is the only moon known to be cloaked in a dense atmosphere,
which is composed mainly of nitrogen. It also has clouds of
methane and ethane, and ongoing research has presented increasing
evidence for methane rain on the large, frigid moon.

Since Titan is veiled in an opaque atmosphere, its surface is
difficult to study with visible light cameras, and only a few
specific infrared wavelengths can penetrate the haze. Cassini's
infrared instruments and radar signals provide an intriguing
glimpse down to the surface of the frozen body, which, as the new
global map reveals, has some interesting Earth-like
features.

"We have created the maps using low-resolution images as a
background with the high-resolution data on top," Le Mouélic
said. "In the few opportunities where we have VIMS imagery from
the closest approach, we can show details as low as 500 meters
[1,640 feet] per pixel. An example of this is from the 47th
flyby, which allowed the observation of the site where the
Huygens descent module landed. This observation is a key one as
it might help us to bridge the gap between the ground truth
provided by Huygens, and ongoing global mapping from orbit, which
will continue up to 2017." [ Video:
Titan's Surprisingly Earth-Like Surface Revealed ]

Cassini arrived in orbit around the ringed planet in July 2004,
and has since made 78 flybys of Titan, the planet's largest moon.
Currently, 48 more flybys are planned from now until the year
2017.

More details coming to light

On all of Cassini's flybys so far, the spacecraft's VIMS
instrument has had only a few opportunities to observe Titan with
high-spatial resolution. As a result, the global map of the moon
shows some areas with more clarity and detail than others, the
researchers said.

Putting together future maps of Titan will also allow scientists
to observe seasonal changes on the surface of Titan and in the
moon's atmosphere. For instance, as the northern hemisphere of
Saturn and its moons shift into spring, some regions of the icy
moon are only now coming into view, Le Mouélic explained.

"Lakes in Titan's northern hemisphere were first discovered by
the RADAR instrument in 2006, appearing as completely smooth
areas," Le Mouélic said. "However, we had to wait up to June 2010
to obtain the first infrared images of the northern lakes,
emerging progressively from the northern winter darkness. The
infrared observations provide the additional opportunity to
investigate the composition of the liquids within the lakes area.
Liquid ethane has already been identified by this means."

Cassini was launched in 1997 and arrived at Saturn in 2004. Last
year, the spacecraft received a
seven-year mission extension that will keep it operational
through 2017.

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